1. Field of the Invention
The present invention relates to a camera having a collapsible mount type photographic optical system and, more particularly, to a zoom camera having a zoom function in which a lens barrel is pulled out and used during photography, and the lens barrel is pushed in and becomes shorter when not in use.
The present invention also relates to a collapsible mount type camera which can change photographic enlargement of a photograph and, in addition, can also change the photographic enlargement of a viewfinder. In particular, it relates to a collapsible type zoom camera having a lens which is closest to the subject and which is movable to a collapsible position received within the camera body and to a lowest magnification position, in which photography is possible. At the position of lowest magnification (a Wide position), the lens is moved closer to the subject than the collapsed position, and the lens is still further movable to a maximum magnification position (a Tele position), which is closer yet to the subject than the lowest magnification position.
2. Description of the Related Art
Cameras are known in the prior art in which a displacement action (when the focal length of the camera is changed to adjust magnification) and a collapsible mount action (when a lens barrel is shortened for periods of non-use) of the photographic optical system are coupled using a cam tube and the like. These types of cameras also have a viewfinder lens and/or light generating unit (strobe), which function as photographic auxiliary units. To achieve a better photograph, it is necessary to change the respective viewfinder magnification or illuminating angle of the light generating unit according to the magnification of the photographic optical system. The variable motions of the photographic auxiliary units are performed by transmitting a rotation of the cam tube and the like via a reduction gear to the photographic auxiliary units.
FIG. 13 is an oblique view showing an embodiment of a prior art camera having a collapsible mount type photographic optical system. As shown in FIG. 13, a motor 52 acting as a drive unit, and gears 53, 54, and 55 acting as a drive force transmission unit, are arranged in a camera 50. The gear 55 is in engagement with a rack portion 56 formed along a circumference of the external circumferential portion of an outer tube 51a of a lens barrel 51.
When the motor 52 rotates, the outer tube 51a of the lens barrel 51 is rotated. Due to the rotation of the outer tube 51a, a photographic optical system (not shown in the drawing), which is disposed in the internal portion of the lens barrel 51, performs a focal length adjustment in order to adjust magnification, moving in a focal length adjustment region (a first region between a Wide position where the lens barrel is shortened and a Tele position where the lens barrel is lengthened) in a direction of an optical axis of the photographic optical system. The photographic optical system also performs a collapsible mount action, moving in a collapsible mount region (a second region between a collapsible mount position where the lens barrel is shortened with the camera being in a period of non-use and the Wide position) in the direction of the optical axis.
The rack portion 56 and engaged gears 57 and 58 are disposed in the camera 50. A gear 58 is in engagement with a gear portion 59d formed in cam portion 59. Plural cam grooves 59a, 59b and 59c are formed in the cam portion 59. Support shafts 61a and 62a of respective viewfinder variable power lenses 61 and 62 and the support shaft 63a of the light generating unit 63, respectively cooperate with the cam grooves 59a, 59b and 59c.
The cam grooves 59a, 59b and 59c have groove portions 59a-1, 59b-1 and 59c-1 in which the respective support shafts 61a, 62a and 63a slide during focal length adjustment (zoom) operation, and groove portions 59a-2, 59b-2 and 59c-2 in which the support shafts 61a, 62a and 63a slide during collapsible mount action of the photographic optical system.
The rotation of the lens barrel 51 is transmitted to the cam portion 59 by means of the rotation of the gears 57 and 58, and the cam portion 59 rotates with the support portion 60 as a fulcrum. Due to this rotation, the support shafts 61a and 62a of the view finder variable power lenses 61 and 62 move along the cam grooves 59a and 59b and, as a result, the viewfinder variable power lenses 61 and 62 move in a direction in which a guide spindle 64 extends, approaching or separating from the fixed viewfinder lenses 66 and 68 and the viewfinder frame 67. Moreover, through the movement of the support shaft 63a of the light generating unit 63 along the cam groove 59c, the light generating unit 63 moves in a direction in which guide spindle 65 extends.
In the prior art collapsible mount type camera of FIG. 13, because the structure couples the rotation of the lens barrel 51 and the rotation of the cam portion 59, the motion of variable power viewfinder lenses 61 and 62 and the light generating unit 63 are not limited to only the focal length adjustment action of the lens barrel 51, but are also linked to the collapsible mount action of the lens barrel 51. Accordingly, in the cam grooves 59a, 59b and 59c, a play region is necessary such that it corresponds to the collapsible mount action of the lens barrel 51. Namely, it is necessary to form the groove portions 59a-2, 59b-2 and 59c-2. Consequently, in order to form this region, the cam portion 59 has to be made large, having the result that the size of the camera is increased.